Preparing for Pathogen X

By Kelly M. Pyrek

The COVID-19 pandemic tested the healthcare sector’s preparedness and left it with lingering questions, including: What relevant scientific information did we possess before the pandemic? Which strategies were successful, and which could be improved? What will the next pandemic look like?  What research will facilitate identification of the next pandemic? And what must be accomplished to prepare for possible pathogens, including unexpected or re-emerging pathogens? (WHO, 2022)

These questions have been among the priorities being addressed in scientific symposia across the globe, as we know it is a matter of when -- not if – another pandemic will strike. The guiding caveat of infectious disease management has been gleaning insights from lessons learned, but it is critical to get out in front of what scientists are calling Pathogen X, which causes Disease X.

As Tahir, et al. (2021) observe, “Some experts have commented that COVID-19, caused by severe acute respiratory coronavirus virus 2 (SARS-CoV-2), met the standards to be considered the first Disease X, while some authors have called Zika a Disease X. However, one unfortunate possibility is that COVID-19 and other recent pandemics might have been milder versions of what will eventually be the most prominent Disease X.”

Banerjee, et al. (2023) note that, “Looking at the ongoing trends, a majority of recent catastrophic onsets have involved RNA viruses, contradictory to the fact that viral pathogens only make up a small component of the pathogens responsible for emerging infectious diseases.” They add, “The transformation from self‐limiting emerging episodes into persistent person‐to‐person transmission is driven by a combination of improved virulence and population dynamics.”

Prior to the COVID-19 pandemic, the World Health Organization (WHO)’s priorities included building on lessons from the Ebola outbreak in West Africa from 2014 to 2016, with a focus on priority pathogens with a consideration of consideration of Disease X, and a research agenda primarily on vaccine development. In late 2015, WHO convened a workshop to identify elements to be used to prioritize diseases and to agree on an initial list of diseases to be urgently addressed under the WHO R&D Blueprint. Of note was the potential for a new infectious disease caused by a novel agent. The outcome of this meeting fed into the prioritization of and research agenda for Disease X.

At the 33rd European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) 2023 conference, WHO presented its methodology for the revision of its 2022-2023 Bacterial Priority Pathogens List (BPPL), which should be issued soon. Currently, the WHO’s the priority diseases are: COVID-19; Crimean-Congo hemorrhagic fever; Ebola virus disease and Marburg virus disease; Lassa fever; Middle East respiratory syndrome coronavirus (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS); Nipah and henipaviral diseases; Rift Valley fever; Zika; and, of course, Disease X.

Last year, WHO also gathered experts in a symposia to tackle what could emerge as Pathogen X/Disease X.

At this WHO meeting, Ombajo (2022) says that characteristics of pathogens with potential to cause pandemic include an appreciable case fatality rate; ongoing risks; efficient human-to-human transmissibility; absence of an effective or widely available treatment/therapeutics/vaccines; immunologically naïve population; ability to evade the immune system; routes of transmission, such as respiratory spread/contact.

Read further from the November 2023 issue HERE